1. Field of the Invention
The present invention relates to a camera, and in particular, to an apparatus and a method of removing image noise in a camera having an illumination sensor.
2. Description of the Related Art
In general, noise generated by a camera sensor, such as a charge coupled device(CCD) sensor, in a camera occurs due to an increase in temperature of the CCD sensor and the artificial amplifications of signals.
It is possible to suppress the image noise by reducing the temperature of a CCD sensor. An expensive digital camera is typically provided with a mechanical cooling means for electronically cooling the CCD sensor in order to reduce the temperature of the CCD sensor. However, an ordinary digital camera is not equipped with such a mechanical cooling system or a CCD sensor cooling device due to costs.
Therefore, in an ordinary digital camera, image noise is removed with the aid of a software instead of a CCD sensor cooling device. A representative method of removing image noise includes capturing an image and then synthesizing the captured image with a file that is fabricated by operating the camera in a state in which the lens is blocked.
The above method is mainly employed as a post-processing algorithm at the final stage as means for providing a high quality image to a user.
In operation, the sensor amplifies signals received by the CCD in order to maintain the brightness of an image to be constant. Because all pixels do not receive the same amount of light, there is a difference in amplification process among the pixels. This is a direct cause of producing glaring noise in a photographed picture or image. It is a noise reduction function that serves to correct the noise produced using the software.
Most of the existing noise reduction algorithms are designed to omnidirectionally perform a smoothing operation within a flat region of an image and to scarcely perform the smoothing at the edge area of an image.
When noise is greatly produced under a low-illumination environment, the noise reduction algorithms can readily remove noise within a flat region of an image. However, the noise at the edge region of the image is not sufficiently removed. As a result, the image acquired using the above method is not satisfactory.
Furthermore, if noise is not removed from a photographed image as stated above, there is a problem in that the compression efficiency for the corresponding image cannot be substantially improved.